1. Field of the Invention
The present invention relates to a sheet loading device having a sheet tray for placing thereon a stack of sheets (sheet stack) to be fed to a given apparatus, and an image forming apparatus using the sheet loading device.
2. Description of the Background Art
Heretofore, there has been known a sheet loading device as disclosed in Japanese Patent Laid-Open Publication No. 2000-153925. This sheet loading device is used for allowing a stack of sheets stored on a sheet loading tray of a sheet cassette detachably attached to an image forming apparatus to be taken out one-by-one and fed to the image forming apparatus. The sheet loading device includes a pair of side fences which are disposed opposed to each other in a sheet-width or lateral direction to uniformly place a sheet stack on the sheet loading tray and adapted to be moved in positive and negative directions so as to change a distance therebetween in conformity to a sheet size.
The side fences are provided, respectively, with a pair of racks which penetrate the sheet loading tray and extend along a bottom surface of the sheet loading tray in mutually opposed directions of the side fences. Further, a pinion is attached to a central region of the bottom surface of the sheet loading tray in such a manner as to be engaged with the racks. Thus, when one of the side fences is laterally moved by a certain distance, the other side fence is moved in an opposite direction by the same distance through the rack of the moved side fence, the pinion and the rack of the other side fence. This provides an easy and convenient manner of positioning the pair of side fences in conformity to a sheet size.
In this type of sheet loading device, when a sheet stack is placed between the side fences while positioning the side fences and then a given sheet load mechanism is driven to load sheets one-by-one from the sheet stack, a lateral distance between the side fences is likely to be increased due to pressure of the sheets caused by a force applied from the sheet load mechanism. The increased lateral distance between the side fences is liable to cause an undesirable situation where the sheet is fed in an oblique posture without being adequately positioned. This tendency becomes prominent when respective axes of a pair of feed rollers are not maintained parallel to each other. The sheet fed in an oblique posture makes it difficult to properly perform an image forming processing therefor.
With a view to eliminate the above disadvantage, in the sheet loading device disclosed in the above patent publication an elastic member is provided in each of the racks in such a manner as to come into press contact with the sheet loading tray in an elastically deformed state so as to generate a frictional force for preventing each of the racks from being lightly moved.
In exchange for this advantage this sheet loading device is required to attach the elastic member to each of the racks. This leads to increases in the number of components and in a process time for assembling thereof, resulting in rising of production costs.